Microelectronic packages and methods therefor

Abstract

A microelectronic package includes a microelectronic element having faces and contacts and a flexible substrate spaced from and overlying a first face of the microelectronic element. The package also includes a plurality of conductive posts extending from the flexible substrate and projecting away from the first face of the microelectronic element, wherein at least some of the conductive posts are electrically interconnected with the microelectronic element, and a plurality of support elements supporting the flexible substrate over the microelectronic element. The conductive posts are offset from the support elements to facilitate flexure of the substrate and movement of the posts relative to the microelectronic element.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This application claims the benefit of the filing date of U.S. Provisional Patent Application No. 60 / 533,210 filed Dec. 30, 2003, entitled “Microelectronic Packages and Methods Therefor,” the disclosure of which is hereby incorporated herein by reference.[0002]The present invention relates to microelectronic packages and to methods of making and testing microelectronic packages.BACKGROUND OF THE INVENTION[0003]Microelectronic devices such as semiconductor chips typically require many input and output connections to other electronic components. The input and output contacts of a semiconductor chip or other comparable device are generally disposed in grid-like patterns that substantially cover a surface of the device (commonly referred to as an “area array”) or in elongated rows which may extend parallel to and adjacent each edge of the device's front surface, or in the center of the front surface. Typically, devices such as chips must be p...

AI Technical Summary

Benefits of technology

The flexible substrate and conductive posts enable reliable testing and connection with standard test boards, reducing costs and improving reliability, while allowing for thermal compensation and high-frequency signal transmission.

Problems solved by technology

Assemblies including packages can suffer from stresses imposed by differential thermal expansion and contraction of the device and the substrate.

Where the terminals of the package are fixed relative to the chip or other device, such as by using solder, these effects tend to cause the terminals to move relative to the contact pads on the circuit board.

This can impose stresses in the solder that connects the terminals to the contact pads on the circuit board.

Testing of packaged devices poses another formidable problem.

However, it is difficult to make connections by pressing the package against a simple test fixture such as an ordinary circuit board having planar contact pads.

For example, in a BGA package, differences in the diameter of the solder balls attached to the terminals, and non-planarity of the chip carrier, may cause some of the solder balls to lie at different heights.

However, such features add to the cost of the test fixture and, in some cases, introduce some unreliability into the test fixture itself.

This is particularly undesirable because the test fixture, and the engagement of the device with the test fixture, should be more reliable than the packaged devices themselves in order to provide a meaningful test.

This requirement imposes constraints on the electrical characteristics of the signal paths in the test fixture, which further complicates construction of the test fixture.

Additionally, when testing packaged devices having solder balls connected with terminals, solder tends to accumulate on those parts of the test fixture that engage the solder balls.

This accumulation of solder residue can shorten the life of the test fixture and impair its reliability.

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